Unique Binary Search Trees

Given n, how many structurally unique BST’s (binary search trees) that store values 1…n?

For example,
Given n = 3, there are a total of 5 unique BST's.

    1         3     3      2      1
     \       /     /      / \      \
      3     2     1      1   3      2
     /     /       \                 \
    2     1         2                 3

Unique Binary Search Trees Solution

public class UniqueBinarySearchTree {
    public int numTrees(int n) {
        int[] dp = new int[n + 1];

        dp[0] = 1;
        dp[1] = 1;

        for(int i = 2; i <= n; i++) {
            for(int j = 1; j <= i; j++) {
                dp[i] += dp[i - j] * dp[j - 1];
            }
        }

        return dp[n];
    }
}